Note 12 - Investments in Affiliates - Summarized Balance Sheet Information for Equity Method Investments (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Current assets		$ 1,545,302	$ 1,376,941	$ 1,493,291
Total assets		2,488,273	2,502,088	2,612,660
Current liabilities		974,593	842,056	876,526
Granite’s share of net assets		76,464	84,176	84,914
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Current assets		116,712	122,348	140,487
Noncurrent assets		165,292	165,331	168,715
Total assets		282,004	287,679	309,202
Current liabilities		48,478	48,322	61,738
Long-term liabilities (1)	[1]	55,206	61,078	60,230
Total liabilities		103,684	109,400	121,968
Net assets		178,320	178,279	187,234
Granite’s share of net assets		$ 76,464	$ 84,176	$ 84,914

[1] The balance primarily relates to debt associated with our real estate investments.